Organic Light Emitting Display Device and Lighting Apparatus for Vehicles Using the Same

ABSTRACT

Disclosed are an organic light emitting display device and lighting apparatus for vehicles using the same. The organic light emitting display device includes a first layer including a first organic layer and a first emission layer on a first electrode, a second layer including a second emission layer and a second organic layer on the first layer, a second electrode on the second layer, and a third organic layer between the first layer and the second layer. A thickness of the first emission layer is equal to or greater than a thickness of each of the first organic layer and the second organic layer.

This application is a continuation of U.S. patent application Ser. No.18/106,911 filed on Feb. 7, 2023, which is a continuation of U.S. patentapplication Ser. No. 17/386,116 filed on Jul. 27, 2021, which is acontinuation of U.S. patent application Ser. No. 16/817,778 filed onMar. 13, 2020, which is a continuation of U.S. patent application Ser.No. 16/145,888 filed on Sep. 28, 2018, which is a divisional of U.S.patent application Ser. No. 15/451,791 filed on Mar. 7, 2017, which is acontinuation of U.S. patent application Ser. No. 15/154,130 filed on May13, 2016, which claims the benefit of Republic of Korea PatentApplication No. 10-2015-0121099 filed on Aug. 27, 2015, each of which ishereby incorporated by reference in its entirety.

BACKGROUND Field of the Invention

The present disclosure relates to an organic light emitting displaydevice, a lighting apparatus for vehicles using the same and amanufacturing method thereof. More particularly, the present disclosurerelates to an organic light emitting display device and a lightingapparatus for vehicles using the same, with enhanced efficiency orlifetime.

Discussion of the Related Art

Recently, as society advances to the information-oriented society, thefield of display devices which visually express an electricalinformation signal is rapidly advancing. Various display devices, havingexcellent performance in terms of thinness, lightness, and low powerconsumption, are being developed correspondingly.

Examples of the display devices include liquid crystal display (LCD)devices, plasma display panel (PDP) devices, field emission display(FED) devices, organic light emitting display devices, etc.

Particularly, organic light emitting display devices are a self-emittingdevice. In comparison with other display devices, organic light emittingdisplay devices have fast response time, high emission efficiency, highluminance, and wide viewing angle, and thus, are attracting muchattention.

Moreover, organic light emitting diodes (OLEDs) applied to organic lightlighting display devices are next-generation light sources having aself-luminance characteristic, and are better in viewing angle,contrast, response time, and power consumption than liquid crystal.Also, OLEDs have a surface emission structure, and thus, are easy toimplement into a flexible type display device.

Recently, researches for using OLEDs as light sources of lighting ordisplay devices are being actively conducted due to their beneficialcharacteristics.

SUMMARY

Accordingly, the present disclosure is directed to an organic lightemitting display device, a lighting apparatus for vehicles using thesame and a method of manufacturing the same that substantially obviateone or more problems due to limitations and disadvantages of the relatedart.

Organic light emitting diodes (OLEDs) each include an emission layerwhich is formed between two electrodes. An electron and a hole areinjected from the two electrodes into the emission layer, and an excitonis generated by combining the electron with the hole. The OLEDs aredevices based on the principle that light is emitted when the generatedexciton is dropped from an excited state to a ground state.

In the emission layer included in each of the OLEDs, a recombinationzone which is an exciton generation zone where an electron and a holeare combined moves from a center zone of the emission layer to anorganic layer adjacent to the emission layer depending on a temperature.For this reason, since the recombination zone of the emission layer isnot located on the emission layer, the emission layer cannot emit light.That is, the emission layer may not contribute to emitting light,causing a reduction in lifetime of organic light emitting displaydevices.

The inventors recognize the above-described problems and have donevarious experiments for improving efficiency or lifetime of an organiclight emitting display device by adjusting a thickness of each of anemission layer and an organic layer which configure the organic lightemitting display device.

Through the various experiments, the inventors have invented an organiclight emitting display device and a lighting apparatus for vehiclesusing the same, which have efficiency or lifetime enhanced by adjustinga thickness of each of an emission layer and an organic layer andmaintain the enhanced efficiency or lifetime at a room temperature or ahigh temperature.

An advantage of the present disclosure is to provide an organic lightemitting display device and a lighting apparatus for vehicles using thesame, with enhanced efficiency or lifetime.

Additional advantages and features of the disclosure will be set forthin part in the description which follows and in part will becomeapparent to those having ordinary skill in the art upon examination ofthe following or may be learned from practice of the disclosure. Theobjectives and other advantages of the disclosure may be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the disclosure, as embodied and broadly described herein, there isprovided an organic light emitting display device that includes a firstlayer including a first organic layer and a first emission layer on afirst electrode, a second layer including a second emission layer and asecond organic layer on the first layer, a second electrode on thesecond layer, and a third organic layer between the first layer and thesecond layer, wherein a thickness of the first emission layer is equalto or greater than a thickness of each of the first organic layer andthe second organic layer.

A thickness of the second emission layer may be equal to or greater thanthe thickness of each of the first organic layer and the second organiclayer.

The first organic layer may include a hole transfer layer, and thesecond organic layer may include an electron transfer layer.

The third organic layer may include at least one among a hole transferlayer, an electron transfer layer, and a charge generation layer.

A sum of the thickness of the first emission layer and a thickness ofthe second emission layer may be equal to or greater than a thickness ofthe third organic layer.

One among the first electrode and the second electrode may include ormay be a semi-transmissive electrode.

The first emission layer and the second emission layer may emit lightshaving at least substantially the same color.

At least one among the first emission layer and the second emissionlayer may include two or more kinds of hosts.

At least one among the first emission layer and the second emissionlayer may include a fluorescent dopant or a phosphorescent dopant.

In another aspect of the present disclosure, there is provided alighting apparatus for vehicles that includes an organic light emittingdevice including an anode, a cathode, and an organic layer and anemission layer between the anode and the cathode, wherein a thickness ofthe emission layer is equal to or greater than a thickness of theorganic layer so that even when an emission zone of the emission layeris moved due to a temperature change of a room temperature environmentand a high temperature environment relevant to a vehicle, the movedemission zone is still located in the emission zone of the emissionlayer.

The emission layer may be provided as one or more.

The one or more emission layers may emit lights having at leastsubstantially the same color.

At least one among the one or more emission layers may include two ormore kinds of hosts.

At least one among the one or more emission layers may include afluorescent dopant or a phosphorescent dopant.

The organic layer may include a first organic layer, a second organiclayer, and a third organic layer.

The first organic layer may be disposed on the anode and may include ahole transfer layer.

The second organic layer may be disposed under the cathode and mayinclude an electron transfer layer.

The third organic layer may be disposed between the first organic layerand the second organic layer and may include at least one among a holetransfer layer, an electron transfer layer, and a charge generationlayer.

The emission layer may include at least one emission layer, and athickness of the at least one emission layer may be equal to or greaterthan a thickness of each of the first organic layer and the secondorganic layer.

The emission layer may include one or more emission layers, and a sum ofthicknesses of the one or more emission layers may be equal to orgreater than a thickness of the third organic layer.

One among the anode and the cathode may include or may be asemitransmissive electrode.

The temperature may be 25° C. to 90° C.

Details of embodiments are included in a detailed description and thedrawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate embodiments of the disclosure andtogether with the description serve to explain the principle of thedisclosure. In the drawings:

FIG. 1 is a diagram illustrating an OLED according to an embodiment ofthe present disclosure;

FIG. 2 is a diagram showing a result obtained by measuring a voltage anda current density with respect to a temperature in an embodiment of thepresent disclosure;

FIG. 3 is a diagram illustrating an emission zone of an emission layerin an embodiment of the present disclosure;

FIG. 4 is a diagram illustrating an OLED according to another embodimentof the present disclosure:

FIG. 5 is a diagram showing lifetime characteristic at a roomtemperature in a comparative example and embodiments of the presentdisclosure;

FIG. 6 is a diagram showing lifetime characteristic at a hightemperature in a comparative example and embodiments of the presentdisclosure; and

FIG. 7 is a diagram illustrating a lighting apparatus for vehiclesaccording to another embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE ILLUSTRA TED EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Advantages and features of the present disclosure, and implementationmethods thereof will be clarified through following embodimentsdescribed with reference to the accompanying drawings. The presentdisclosure may, however, be embodied in different forms and should notbe construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the present disclosureto those skilled in the art. Further, the present disclosure is onlydefined by scopes of claims.

A shape, a size, a ratio, an angle, and a number disclosed in thedrawings for describing embodiments of the present disclosure are merelyan example, and thus, the present disclosure is not limited to theillustrated details. Like reference numerals refer to like elementsthroughout. In the following description, when the detailed descriptionof the relevant known function or configuration is determined tounnecessarily obscure the important point of the present disclosure, thedetailed description will be omitted. In a case where ‘comprise’,‘have’, and ‘include’ described in the present specification are used,another part may be added unless ‘only-’ is used. The terms of asingular form may include plural forms unless referred to the contrary.

In construing an element, the element is construed as including an errorrange although there is no explicit description.

In describing a position relationship, for example, when a positionrelation between two parts is described as ‘on˜’, ‘over˜’, ‘under˜’, and‘next˜’, one or more other parts may be disposed between the two partsunless ‘just’ or ‘direct’ is used.

In describing a time relationship, for example, when the temporal orderis described as ‘after˜’, ‘subsequent˜’. ‘next˜’, and ‘before˜’, a casewhich is not continuous may be included unless ‘just’ or ‘direct’ isused.

It will be understood that, although the terms “first”. “second”, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure.

Features of various embodiments of the present disclosure may bepartially or overall coupled to or combined with each other, and may bevariously inter-operated with each other and driven technically as thoseskilled in the art can sufficiently understand. The embodiments of thepresent disclosure may be carried out independently from each other, ormay be carried out together in co-dependent relationship.

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings.

FIG. 1 is a diagram illustrating an OLED 100 according to an embodimentof the present disclosure.

Referring to FIG. 1 , the OLED 100 according to an embodiment of thepresent disclosure may include a substrate 101, first and secondelectrodes 102 and 104, and a plurality of organic layers 120, 130, 140and 150 between the first and second electrodes 102 and 104.

The first electrode 102 may be an anode that supplies a hole, and thesecond electrode 104 may be a cathode that supplies an electron.

A hole injection layer (HIL) 120, a hole transport layer (HTL) 130, anemission layer (EML) 140 and an electron transport layer (ETL) 150,which are organic layers, may be formed on the first electrode 102.

The HIL 120 enables a hole supplied from the first electrode 102 to besmoothly injected into the HTL 130.

The HTL 130 may supply a hole supplied from the HIL 120 to the emissionlayer 140. The ETL 150 may supply an electron supplied from the secondelectrode 104 to the emission layer 140. As a result, the hole suppliedthrough the HTL 130 and the electron supplied through the ETL 150 may berecombined in the emission layer 140 to generate an exciton. A zonewhere the exciton is generated in the emission layer 140 may be referredto as a recombination zone or an emission zone (or an emission area).The emission layer 140 may contribute to emit light when therecombination zone is disposed in the emission layer 140.

The organic layers such as the emission layer 140, the HIL 120, the HTL130, and the ETL 150 are affected by a change in temperature. Also, whenan OLED is applied to a lighting apparatus for vehicles, the OLED isaffected by an external environment temperature, and thus, the organiclayers included in the OLED are further affected by the externalenvironment temperature. This will now be described in detail withreference to FIG. 2 .

FIG. 2 is a diagram showing results obtained by measuring voltage andcurrent density with reference to temperature according to an embodimentof the present disclosure, wherein the abscissa axis indicates a voltage(V) and the ordinate axis indicates a current density (mA/cm²). The OLEDmay be loaded into a chamber, and then, a temperature of the chamber maybe changed to −20° C., 0° C. 25° C., 45° C., 65° C., and 85° C. In thesestates, an OLED may be stabilized for about one hour to two hours, andthen, the voltage and the current density are measured. The results ofthe measurement are shown in FIG. 2 .

As shown in FIG. 2 , when a temperature of the OLED increases, a chargemobility of an organic layer included in the OLED increases quickly, andat a low temperature, the charge mobility of the organic layer isreduced to cause an increase in a voltage. As a result, a charge balancewhich is a balance of electrons and holes is broken at a temperaturelower or higher than a room temperature (25° C.), and a generation zone(the recombination zone or the emission zone) where an exciton isgenerated by combining an electron with a hole may move from theemission layer to the organic layer. For this reason, the emission layermay not emit light in a desired emission zone. This will now bedescribed in detail with reference to FIG. 3 .

FIG. 3 is a diagram illustrating an emission zone of an emission layeraccording to an embodiment of the present disclosure.

When a temperature of the OLED increases, a hole mobility of the HTL 130and an electron mobility of the ETL 150 increase. At this time, amobility of a charge having a relative high speed increases further, andfor this reason, a charge balance which is a balance of previouslygenerated electrons and holes is broken.

Generally, when a temperature of the OLED increases, a hole mobility ofthe HTL 130 increases due to characteristics of the organic layer, andthe emission zone or the recombination zone RZ may be provided in aboundary between the emission layer 140 and the ETL 150 instead of theemission layer 140.

As illustrated in FIG. 3 , when the recombination zone RZ is provided ina boundary between the emission layer 140 and the ETL 150 instead of theemission layer 140, an exciton may not contribute to emitting light, andlight energy which is to be dissipated through emission of light ischanged to thermal transition. If the light energy is changed to thethermal transition, degradation of the OLED is accelerated, causing areduction in lifetime of the OLED.

Even when the temperature changes from such a high temperature back tothe room temperature, the lifetime of the OLED is reduced at the roomtemperature because the OLED has been already degraded at the hightemperature. On the other hand, if the electron mobility of the ETL 150increases, the emission zone or the recombination zone RZ is provided inthe HTL 130 or a boundary between the emission layer 140 and the HTL 130instead of the emission layer 140. As a result, if the recombinationzone RZ is provided in the HTL 130 or a boundary between the emissionlayer 140 and the HTL 130 instead of the emission layer 140, an excitonmay not contribute to emitting light, and light energy which is to bedissipated through emission of light is changed to thermal transition.If the light energy is changed to the thermal transition, degradation ofthe OLED is accelerated, causing a reduction in lifetime of the OLED.

To address such a problem, in an organic light emitting display deviceand a lighting apparatus for vehicles using the same according to anembodiment of the present disclosure, a thickness of an emission layerand a thickness of an organic layer are adjusted to enhance efficiencyor lifetime of the organic light emitting display device at the roomtemperature or a high temperature.

FIG. 4 is a diagram illustrating an OLED 200 according to anotherembodiment of the present disclosure.

Referring to FIG. 4 , the OLED 200 may include a substrate 201, firstand second electrodes 202 and 204, and a plurality of organic layers210, 230 and 250 and a plurality of emission layers 241 and 242 betweenthe first and second electrodes 202 and 204. That is, the OLED 200 mayinclude a first layer including a first organic layer 210 and a firstemission layer 241 on the first electrode 202, a second layer includinga second emission layer 242 and a second organic layer 250 on the firstlayer, the second electrode 204 on the second layer, and a third organiclayer 230 between the first layer and the second layer.

The substrate 201 may be formed of an insulating material or a materialhaving flexibility. The substrate 201 may be formed of glass, metal,plastic, and/or the like, but is not limited thereto. If an organiclight emitting display device is a flexible organic light emittingdisplay device, the substrate 201 may be formed of a flexible materialsuch as plastic and/or the like. Also, if an organic light emittingdevice which is easy to realize flexibility is applied to a lightingdevice for vehicles, various designs and a degree of freedom of designof a light device for vehicles are secured according to a structure oran appearance of a vehicle.

The first electrode 202 is an anode that supplies a hole, and may beformed of indium tin oxide (ITO), indium zinc oxide (IZO), or the likewhich is a transparent conductive material such as transparentconductive oxide (TCO). However, the present embodiment is not limitedthereto. Alternatively, the first electrode 202 may be formed of gold(Au), silver (Ag), aluminum (Al), molybdenum (Mo), magnesium (Mg),Lithium (Li), calcium (Ca), lithium fluoride (LiF), Ag—Mg, ITO, IZO,and/or the like, may be formed of an alloy thereof, or may be formed ofa single layer or a multilayer. However, the present embodiment is notlimited thereto.

Moreover, the first electrode 202 may include a reflective layer inorder for light L, emitted from each of the emission layers 241 and 242,not to be irradiated in a down direction through the first electrode202. In detail, the first electrode 202 may have a three-layeredstructure where a first transparent layer, a reflective layer, and asecond transparent layer are sequentially stacked. The first transparentlayer and the second transparent layer may each be formed of TCO such asITO. IZO, or the like. The reflective layer between two the transparentlayers may be formed of a metal material such as copper (Cu), silver(Ag), palladium (Pd), or the like. For example, the first electrode 202may be formed of ITO/Ag/ITO. Alternatively, the first electrode 202 mayhave a two-layered structure where a transparent layer and a reflectivelayer are stacked.

The second electrode 204 is a cathode that supplies an electron, and maybe formed of Au, Ag, Al, Mo, Mg, Li, Ca, LiF, ITO, IZO, Ag—Mg, and/orthe like, or may be formed of an alloy thereof. The second electrode 204may be formed with a single layer or multiple layers. However, thepresent embodiment is not limited thereto.

Each of the first electrode 202 and the second electrode 204 may bereferred to as an anode or a cathode. Alternatively, the first electrode202 may be formed as a transmissive electrode, and the second electrode204 may be formed as a semi-transmissive electrode. Alternatively, thefirst electrode 202 may be formed as a reflective electrode, and thesecond electrode 204 may be formed as a semi-transmissive electrode.Alternatively, the first electrode 202 may be formed as asemi-transmissive electrode, and the second electrode 204 may be formedas a transmissive electrode. Alternatively, at least one among the firstand second electrodes 202 and 204 may be formed as a semi-transmissiveelectrode.

Moreover, a capping layer may be further formed on the second electrode204, for protecting the OLED. Also, the capping layer may be omitteddepending on the structure or characteristic of the OLED.

A first organic layer 210, a second organic layer 250, and a thirdorganic layer 230 which are the organic layers may be disposed on thefirst electrode 202.

The first organic layer 210 may be disposed on the first electrode 202.The first organic layer 210 may be formed as a hole transfer layer whichinjects a hole or transfers the hole. For example, the hole transferlayer which is the first organic layer 210 may be formed of at least onelayer of an HIL and an HTL. Alternatively, the first organic layer 210may be formed of two or more HILs. Alternatively, the first organiclayer 210 may be formed of two or more HTLs. Alternatively, the firstorganic layer 210 may be formed of an HIL and an HTL.

Moreover, the first organic layer 210 may be formed with multiple layerscapable of being doped. A doping material may be an organic material oran inorganic material and may include metal.

For example, the HTL may be formed of2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ), coppercomplex (CuPc), and/or the like, but is not limited thereto.

For example, the HTL may be formed ofN,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine(NPD), N,N′bis(naphthalene-1-yl)-N,N′-bis(phenyl)-benzidine (NPB),N,N′Obis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine (TPD), and/or thelike, but is not limited thereto.

The second organic layer 250 may be disposed under the second electrode204. The second organic layer 250 may be formed as an electron transferlayer which injects an electron or transfers the electron. For example,the electron transfer layer which is the second organic layer 250 may beformed of at least one layer of an EIL and an ETL. Alternatively, thesecond organic layer 250 may be formed of two or more EILs.Alternatively, the second organic layer 250 may be formed of two or moreETLs. Alternatively, the second organic layer 250 may be formed of anEIL and an ETL.

Moreover, the second organic layer 250 may be formed with multiplelayers capable of being doped. A doping material may be an organicmaterial or an inorganic material and may include metal.

For example, the EIL may be formed of LiF and/or the like, but is notlimited thereto.

For example, the ETL may be formed oftris(8-hydroxy-quinolonato)aluminum (Alq₃),8-hydroxyquinolinolato-lithium (Liq), and/or the like, but is notlimited thereto.

The third organic layer 230 may be disposed between the first layerincluding the first organic layer 210 and the first emission layer 241,and the second layer including the second emission layer 242 and thesecond organic layer 250. The third organic layer 230 may include atleast one among an electron transfer layer that injects or transfers anelectron, a hole transfer layer that injects or transfers a hole, and acharge generation layer (CGL) that generates the electron or the hole.The electron transfer layer may include one among an EIL and an ETL.Alternatively, the electron transfer layer may include one among an EILthat injects an electron, an ETL that transports the electron, and anN-type CGL that generates the electron. The hole transfer layer mayinclude one among an HIL and an HTL. Alternatively, the hole transferlayer that injects, transfers, or generates a hole may include one amongan HIL, an HTL, and a P-type CGL. Also, the CGL may include one amongthe N-type CGL and the P-type COL. Therefore, the third organic layer230 may include at least one among an EIL, an ETL, an HIL, an HTL, anN-type CGL, and a P-type CGL.

When the electron transfer layer includes one among the EIL, the ETL,and the N-type CGL and the hole transfer layer includes one among theHIL, the HTL, and the P-type COL, the electron transfer layer and holetransfer layer of the third organic layer 230 may be disposed adjacentto each other and may have a PN junction. As a result, the third organiclayer 230 may include the ETL, the N-type CGL, the P-type CGL, and theHTL which are disposed on the first EML 241.

Moreover, the third organic layer 230 may be formed with multiple layerscapable of being doped. A doping material may be an organic material oran inorganic material and may include metal.

For example, the HTL may be formed of2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ), coppercomplex (CuPc), and/or the like, but is not limited thereto.

For example, the HTL may be formed ofN,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine(NPD), N,N′bis(naphthalene-1-yl)-N,N′-bis(phenyl)-benzidine (NPB),N,N′Obis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine (TPD), and/or thelike, but is not limited thereto.

For example, the EIL may be formed of LiF and/or the like, but is notlimited thereto.

For example, the ETL may be formed oftris(8-hydroxy-quinolonato)aluminum (Alq₃),8-hydroxyquinolinolato-lithium (Liq), and/or the like, but is notlimited thereto.

The N-type CGL may inject an electron into the first EML 241. The N-typeCGL may be formed as an organic layer which is doped with alkali metalsuch as lithium (Li), sodium (Na), potassium (K), or cesium (Cs) oralkali earth metal such as magnesium (Mg), strontium (Sr), barium (Ba),or radium (Ra), but is not limited thereto.

The P-type CGL included in the third organic layer 230 may inject a holeinto the second EML 242. The P-type CGL may be formed as an organiclayer including a P-type dopant, but is not limited thereto.

The first organic layer 210 may supply a hole, supplied from the firstelectrode 202, to the first EML 241. The electron transfer layer or theCGL included in the third organic layer 230 may supply an electron,supplied from the second electrode 204, to the first EML 241. As aresult, the hole supplied through the first organic layer 210 and theelectron supplied through the third organic layer 230 may be recombinedin the first EML 241 to generate an exciton. A zone where the exciton isgenerated in the first EML 241 may be referred to as a recombinationzone or an emission zone (or an emission area).

The hole transfer layer or the CGL included in the third organic layer230 may supply the hole, supplied from the first electrode 202, to thesecond EML 242. The second organic layer 250 may supply the electron,supplied from the second electrode 204, to the second EML 242. As aresult, the hole supplied through the third organic layer 230 and theelectron supplied through the second organic layer 250 may be recombinedin the second EML 242 to generate an exciton. A zone where the excitonis generated in the second EML 242 may be referred to as a recombinationzone or an emission zone (or an emission area).

The first EML 241 and the second EML 242 may be emission layers thatemit lights having at least substantially the same color, respectively.For example, the first EML 241 and the second EML 242 may be one among ared EML, a green EML, and a blue EML. As a result, the OLED according toan embodiment of the present disclosure may be a mono light emittingdevice that emits lights having at least substantially the same color.

Moreover, the first EML 241 and the second EML 242 may each include atleast one host and at least one dopant. The at least one host mayinclude a host having hole characteristic or a host having electroncharacteristic. Alternatively, the at least one host may be a mixed hostincluding two or more kinds of hosts. When the at least one hostincludes two or more kinds of hosts, the at least one host may include ahost having hole characteristic and a host having electroncharacteristic. Also, the at least one dopant may be a fluorescentdopant or a phosphorescent dopant.

When each of the first EML 241 and the second EML 242 is the red EML,the at least one host may include one or more host materials, andexamples of the host materials may include4,4′bis(carbazol-9-yl)biphenyl (CBP), 1,3-bis(carbazol-9-yl)benzene(MCP),N,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine(NPD), Be complex, and/or the like. The at least one dopant may includea phosphorescent dopant, and examples of the phosphorescent dopant mayincludebis(2-benzo[b]thiophen-2-yl-pyridine)(acetylacetonate(iridium(III))(Ir(btp)₂(acac)), bis(1-phenylisoquinoline)(acetylacetonate)iridium(III)(Ir(piq)₂(acac)), tris(1-phenylquinoline)iridium(III) (Ir(piq)₃),5,10,15,20-tetraphenyltetrabenzoporphyrin platinum complex (Pt(TPBP)),and/or the like. Alternatively, the at least one dopant may be afluorescent dopant, and examples of the fluorescent dopant may includeperylene and/or the like. The host material or the dopant materialconstituting the red EML does not limit details of the presentdisclosure.

When each of the first EML 241 and the second EML 242 is the green EML,the at least one host may include one or more host materials, andexamples of the host materials may include4,4′bis(carbazol-9-yl)biphenyl (CBP), 1,3-bis(carbazol-9-yl)benzene(MCP),N,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine(NPD), Be complex, and/or the like. The at least one dopant may be aphosphorescent dopant, and examples of the phosphorescent dopant mayinclude tris(2-phenylpyridine)iridium(III) (Ir(ppy)₃),Bis(2-phenylpyridine)(acetylacetonato)iridium(III) (Ir(ppy)₂(acac)),and/or the like. Alternatively, the at least one dopant may be afluorescent dopant, and examples of the fluorescent dopant may includetris(8-hydroxyquinolino)aluminum (Alq₃) and/or the like. The hostmaterial or the dopant material constituting the green EML does notlimit details of the present disclosure.

When each of the first EML 241 and the second EML 242 is the blue greenEML, the at least one host may include one or more host materials, andexamples of the host materials may include4,4′bis(carbazol-9-yl)biphenyl (CBP), 1,3-bis(carbazol-9-yl)benzene(MCP), 9,10-di(naphth-2-yl)anthracene (AND), and/or the like. The atleast one dopant may be a phosphorescent dopant, and examples of thephosphorescent dopant may include(Bis[2-(4,6-difluorophenyl)pyridinato-N]picolinato)iridium(III) (FIrpic)and/or the like. Alternatively, the at least one dopant may be afluorescent dopant, and examples of the fluorescent dopant may includepolyfluorene (PFO)-based polymer, polyphenylenevinylene (PPV)-basedpolymer, and/or the like. The host material or the dopant materialconstituting the blue EML does not limit details of the presentdisclosure.

In another embodiment of the present disclosure, the emission layer maybe configured to have a thickness that is equal to or greater than thatof each of the organic layers, for enhancing efficiency or lifetime ofthe OLED at the room temperature or a high temperature. Also, theemission layer may be configured to have a thickness that is equal to orgreater than that of each of the organic layers, irrespective of thenumber of the organic layers or the emission layers configuring theOLED. This will now be described in detail with reference to Table 1 andFIGS. 5 and 6 .

Table 1 shows a result which is obtained by measuring the efficienciesand color coordinates of comparative examples 1 and 2 and theefficiencies and color coordinates of embodiments 1 and 2 of the presentdisclosure. The efficiencies have been measured at the room temperatureof 25° C.

TABLE 1 Efficiency (Cd/A) CIEx CIEy Comparative 57 0.684 0.312 Example 1Comparative 84 0.682 0.316 Example 2 Embodiment 1 80.5 0.686 0.312Embodiment 2 82.1 0.686 0.312

Referring to Table 1, in comparative example 1, a first electrode isformed on a substrate, and a first organic layer, an emission layer, anda third organic layer are formed on the first electrode. Also, a secondelectrode is formed on the third organic layer, and a capping layer isformed for protecting an OLED. The first organic layer is formed ofN,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine(NPD), a zone adjacent to the substrate is doped with2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ), and athickness of the first organic layer is adjusted to 230 nm. Also, theemission layer is formed as a red EML. The emission layer includes Becomplex as a host material, andbis(2-benzo[b]thiophen-2-yl-pyridine)(acetylacetonate(iridium(III))(Ir(btp)₂(acac)) as a dopant. A thickness of the emission layer isadjusted to 30 nm. The third organic layer is formed oftris(8-hydroxy-quinolinato)aluminum (Alq₃) and8-hydroxyquinolinolato-lithium (Liq), and a thickness of the thirdorganic layer is adjusted to 30 nm. The capping layer is formed ofN,N′-bis(naphthalene-1-yl)-N,N′bis(phenyl)-2,2′-dimethylbenzidine (NPD).Here, the materials of the first organic layer, the emission layer, thethird organic layer, and the capping layer do not limit details of thepresent disclosure.

In comparative example 2, a first electrode is formed on a substrate,and a first organic layer, a first EML, a third organic layer, a secondEML, and a second organic layer are formed on the first electrode. Asecond electrode is formed on the second organic layer, and a cappinglayer is formed for protecting an OLED. Each of the first organic layer,the first EML, and the capping layer is formed of the same material as amaterial applied to the comparative example 1. Also, each of the firstEML and the second EML is formed as a red EML. A thickness of the firstorganic layer is adjusted to 85 nm, and a thickness of the first EML isadjusted to 30 nm. Also, the third organic layer is an electron transferlayer and is formed of oxadiazole, a zone adjacent to a hole transferlayer of the third organic layer is doped with Li and a thickness of theelectron transfer layer is adjusted to 25 nm. Also, the third organiclayer is a hole transfer layer and is formed of NPD, a zone adjacent tothe hole transfer layer of the third organic layer is doped withF4-TCNQ, and a thickness of the hole transfer layer is adjusted to 90nm. Therefore, a thickness of the third organic layer is adjusted to 115nm. The second EML includes Be complex as a host material (for example,and/or the like) and Ir(btp)₂(acac) as a dopant, and a thickness of thesecond EML is adjusted to 30 nm. The second organic layer is formed ofAlq₃ and Liq, and a thickness of the second organic layer is adjusted to30 nm. Here, the materials of the first organic layer, the first EML,the third organic layer, the second EML, the second organic layer, andthe capping layer do not limit details of the present disclosure.

In embodiment 1, a first electrode is formed on a substrate, and a firstorganic layer, a first EML, a third organic layer, a second EML, and asecond organic layer are formed on the first electrode. A secondelectrode is formed on the second organic layer, and a capping layer isformed for protecting an OLED. The embodiment 1 is configuredidentically to the comparative example 2 and uses the same materials asmaterials applied to the comparative example 2. A thickness of the firstorganic layer is 45 nm, and a thickness of the first EML is 70 nm. Athickness of the third organic layer is 75 nm. A thickness of the secondEML is 70 nm, and a thickness of the second organic layer is 30 nm.Here, the materials of the first organic layer, the first EML, the thirdorganic layer, the second EML, the second organic layer, and the cappinglayer do not limit details of the present disclosure.

In embodiment 2, a first electrode is formed on a substrate, and a firstorganic layer, a first EML, a third organic layer, a second EML, and asecond organic layer are formed on the first electrode. A secondelectrode is formed on the second organic layer, and a capping layer isformed for protecting an OLED. The embodiment 2 is configuredidentically to the embodiment 1 and uses the same materials as materialsapplied to the embodiment 1. Also, a host of each of the first andsecond EMLs may be a mixed host. The host of each of the first andsecond EMLs includes Be complex and NPD, and a dopant of each of thefirst and second EMLs includes Ir(btp)₂(acac). When the host included ineach of the first and second EMLs is the mixed host instead of a singlehost, a charge balance of each of the first and second EMLs may beadjusted. Also, when each of the first and second EMLs is formed of themixed host, it is easy to adjust a charge balance when a thickness ofeach of the first and second EMLs is thickened. A thickness of the firstorganic layer is 45 nm, and a thickness of the first EML is 70 nm. Athickness of the third organic layer is 75 nm. A thickness of the secondEML is 70 nm, and a thickness of the second organic layer is 30 nm.Here, the materials of the first organic layer, the first EML, the thirdorganic layer, the second EML, the second organic layer, and the cappinglayer do not limit details of the present disclosure.

As shown in Table 1, the efficiency is further enhanced in embodiments 1and 2 as compared with comparative example 1. That is, it can be seenthat the efficiency of comparative example 1 is 57 Cd/A, the efficiencyof embodiment 1 is 80.5 Cd/A. and the efficiency of embodiment 2 is 82.1Cd/A. It can be also seen that the efficiencies of embodiments 1 and 2are similar to that of comparative example 2.

Color coordinates represent red color coordinates. To describe colorcoordinates (CIEx, CIEy), it can be seen that in the comparativeexamples and the embodiments, the color coordinates are not changeddespite a thickness difference between the organic layers. Through this,when a thickness of the first EML or a thickness of the second EML isequal to or greater than that of each of the first and second organiclayers, the color coordinates are not changed despite the thicknessdifference between the organic layers, and thus, it can be seen that adesired color is realized. Alternatively, when a sum of a thickness ofthe first EML and a thickness of the second EML is equal to or greaterthan that of the third organic layer, the color coordinates are notchanged despite the thickness difference between the organic layers, andthus, it can be seen that a desired color is realized.

The results which are obtained by measuring lifetime characteristic atthe room temperature and a high temperature will be described below withreference to FIGS. 5 and 6 .

FIG. 5 is a diagram showing lifetime characteristic at a roomtemperature in a comparative example and embodiments of the presentdisclosure.

In FIG. 5 , the abscissa axis indicates a time (hr), and the ordinateaxis indicates a luminance drop rate (%). Also, FIG. 5 shows the resultsthat are obtained by measuring lifetime characteristic at the roomtemperature of 25° C.

As shown in FIG. 5 , the lifetime characteristic is further enhanced incomparative example 2 and embodiments 1 and 2 as compared withcomparative example 1 with respect to a time (i.e., 95% lifetime (T95)of an OLED) taken until the emission luminance corresponding to 95% ofan initial emission luminance is obtained.

In addition, it can be seen that a luminance drop rate is rapidlylowered with time in comparative example 1 in comparison withcomparative example 2 and embodiments 1 and 2. Also, it can be seen thatluminance drop rates are almost similar with time in comparative example2 and embodiments 1 and 2. As a result, it can be seen that when athickness of an emission layer is greater than that of an organic layer,lifetime is enhanced. That is, it can be seen that when a thickness of afirst EML or a thickness of a second EML is equal to or greater thanthat of each of first and second organic layers, lifetime is enhanced.Also, it can be seen that when a sum of a thickness of the first EML anda thickness of the second EML is equal to or greater than that of athird organic layer, lifetime is enhanced.

Moreover, in comparative example 2 where a thickness of the emissionlayer is less than that of the organic layer, it can be seen that thelifetime characteristic at the room temperature is secured. In a case ofa high temperature, when injection of an electron and a hole and amobility of each of the electron and the hole are changed to move arecombination zone that is an exciton generation zone, the recombinationzone may be located in the organic layer adjacent to the emission layerwithout being located in the emission layer. When light is emitted fromthe organic layer adjacent to the emission layer, the emission layer maynot contribute to emitting the light, and light energy which is to bedissipated through emission of the light is changed to thermaltransition. If the light energy is changed to the thermal transition,deterioration of the OLED is accelerated, causing a reduction inlifetime of the OLED. As a result, according to an embodiment of thepresent disclosure, a thickness of the emission layer may be equal to orgreater than that of the organic layer, and thus, even when therecombination zone is moved because a charge balance is changed due to achange in mobility or injection of an electron or a hole at the roomtemperature or the high temperature, the recombination zone may belocated in the emission layer, thereby providing an organic lightemitting display device or a lighting device for vehicles, whichmaintains enhanced reliability or stability at the room temperature orthe high temperature. Lifetime characteristic at a high temperature willbe described below with reference to FIG. 6 .

FIG. 6 is a diagram showing lifetime characteristic at a hightemperature in a comparative example and embodiments of the presentdisclosure.

In FIG. 6 , the abscissa axis indicates a time (hr), and the ordinateaxis indicates a luminance drop rate (%). FIG. 6 shows the results thatare obtained by measuring lifetime characteristic at 60° C. The resultsof the measurement may be similar to lifetime characteristic at 85° C.

A temperature range desired by the organic light emitting display devicemay be a range of 60° C. to 90° C. The temperature range may be referredto as a temperature range which enables the OLED to endure in a processof manufacturing the organic light emitting display device, and may bechanged depending on a manufacturing process condition. Also, when thetemperature range is applied to a lighting apparatus for vehicles, thetemperature range may be a range of −40° C. to 90° C. depending on atemperature change of an external environment.

As shown in FIG. 6 , the lifetime characteristic is further enhanced inembodiments 1 and 2 as compared with comparative examples 1 and 2 withrespect to a time (i.e., 90% lifetime (T90) of an OLED) taken until theemission luminance corresponding to 90% of an initial emission luminanceis obtained. Also, in a case of measuring 95% lifetime (T95) of the OLEDas in FIG. 5 , lifetime is rapidly reduced in comparative examples 1 and2, and thus, in order to address a problem where it is difficult tocheck a measurement result of lifetime characteristic. FIG. 6 shows theresults which are obtained by measuring 90% lifetime (T90) of the OLED.

In embodiments 1 and 2, since a thickness of an emission layer is equalto or greater than that of each of organic layers, it can be seen thatin a case where the OLED is driven at a high temperature, even when arecombination zone or an emission zone of the emission layer is moved,the recombination zone or the emission zone is still located in theemission layer, and thus, lifetime is enhanced. Also, it can be seenthat lifetime is further enhanced in embodiment 2, to which a mixed hostis applied, than embodiment 1. Since a charge balance of the emissionlayer is adjusted by the mixed host, it can be seen that a luminancedrop rate with respect to a time is low, and lifetime is enhanced.

Moreover, it can be seen that lifetime characteristic at a hightemperature is further degraded in comparative example 2 thanembodiments 1 and 2. As a result, since a thickness of the emissionlayer is equal to or greater than that of each of the organic layers, itcan be seen that in a case where the OLED is driven at the roomtemperature or the high temperature, even when the recombination zone oremission zone of the emission layer is moved, the recombination zone orthe emission zone is still located in the emission layer, and thus,lifetime is enhanced.

Also, it can be seen that a temperature range corresponding to the roomtemperature or the high temperature may be a temperature range of 25° C.to 90° C., and lifetime of the organic light emitting display device orthe lighting apparatus for vehicles according to an embodiment of thepresent disclosure is enhanced within a temperature range of 25° C. to90° C. Also, since lifetime at the high temperature is enhanced, it canbe seen that the high-temperature stability of the organic lightemitting display device or the lighting apparatus for vehicles isenhanced.

FIG. 7 is a diagram illustrating a vehicle lighting apparatus Lincluding an OLED according to another embodiment of the presentdisclosure.

The vehicle lighting apparatus L of FIG. 7 may be mounted on a frontsurface or a rear surface of a vehicle and may secure a front view or arear view of a driver when the vehicle is driving. The vehicle lightingapparatus L according to another embodiment of the present disclosuremay be at least one among headlights, a high beam, taillights, a brakelight, a back-up light, a fog lamp, a turn signal light, and anauxiliary lamp, but is not limited thereto. Alternatively, the vehiclelighting apparatus L may be applied to all indicator lamps which areused to secure a field of view of a driver and transmit or receive asignal of a vehicle. FIG. 7 does not limit vehicle lighting applied tothe vehicle lighting apparatus L according to the present embodiment.

The vehicle lighting apparatus L according to the present embodiment mayinclude an OLED D, may surface-emit light, and may have a flexiblestructure. The OLED D included in the vehicle lighting apparatus L mayhave the structure described above with reference to FIGS. 4 to 6 . TheOLED D may include a substrate, first and second electrodes, and aplurality of organic layers and a plurality of emission layers betweenthe first and second electrodes. That is, the OLED D may include a firstlayer including a first organic layer and a first EML on the firstelectrode, a second layer including a second EML and a second organiclayer on the first layer, the second electrode on the second layer, anda third organic layer between the first layer and the second layer.

In the OLED D, in a case where a thickness of the first EML or athickness of the second EML is equal to or greater than that of each ofthe first and second organic layers, when a vehicle drives at the roomtemperature or a high temperature, a recombination zone or an emissionzone which is an exciton generation zone where an electron and a holeare recombined to generate an exciton may be located in the emissionlayer. Also, in a case where a sum of a thickness of the first EML and athickness of the second EML is equal to or greater than that of thethird organic layer, when the vehicle drives at the room temperature orthe high temperature, the recombination zone or the emission zone whichis the exciton generation zone where the electron and the hole arerecombined to generate the exciton may be located in the emission layer.Accordingly, provided is a lighting apparatus for vehicles, whichmaintains enhanced lifetime when a vehicle drives at the roomtemperature or the high temperature.

As described above, according to the embodiments of the presentdisclosure, the emission layer may be configured to have a thicknessthat is equal to or greater than that of each of the organic layers,thereby providing an organic light emitting display device or a lightingapparatus for vehicles, with enhanced efficiency or lifetime at a roomtemperature or a high temperature.

Moreover, according to the embodiments of the present disclosure, sincethe OLED is configured in a structure where a thickness of the emissionlayer is equal to or greater than that of each of the organic layers,the emission zone of the emission layer is maintained in the emissionlayer despite a change.

Moreover, the organic light emitting display device or the lightingapparatus for vehicles according to the embodiments of the presentdisclosure maintains enhanced lifetime at a high temperature and securessafety at a high temperature.

The details of the present disclosure described in technical problem,technical solution, and advantageous effects do not specify essentialfeatures of claims, and thus, the scope of claims is not limited by thedetails described in detailed description of the disclosure.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the disclosure. Thus, itis intended that the present disclosure covers the modifications andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An organic light emitting display device,comprising: a first electrode on a substrate; a first organic layer onthe first electrode; a first emission layer on the first organic layer;a second emission layer on the first emission layer; a second organiclayer on the second emission layer; a third organic layer between thefirst emission layer and the second emission layer; and a secondelectrode on the second organic layer; wherein the third organic layercomprises a first electron transport layer and the second organic layercomprises a second electron transport layer, and wherein a thickness ofthe first emission layer or a thickness of the second emission layer isequal to or greater than each of a thickness of the first electrontransport layer and a thickness of the second electron transport layer.2. The organic light emitting display device of claim 1, wherein thefirst emission layer and the second emission layer emit light having atleast a substantially same color.
 3. The organic light emitting displaydevice of claim 2, wherein each of the first emission layer and thesecond emission layer comprises a blue emission layer.
 4. The organiclight emitting display device of claim 1, further comprising: a cappinglayer on the second electrode.
 5. The organic light emitting displaydevice of claim 4, wherein the capping layer comprisesN,N′-bis(naphthalene-1-yl)-N,N′bis(phenyl)-2,2′-dimethylbenzidine (NPD).6. The organic light emitting display device of claim 1, wherein thesubstrate comprises a material having flexibility.
 7. The organic lightemitting display device of claim 1, wherein the first electrode includesa plurality of layers comprising at least one of indium tin oxide (ITO),indium zinc oxide (IZO), gold (Au), silver (Ag), aluminum (Al),molybdenum (Mo), magnesium (Mg), lithium (Li), calcium (Ca), lithiumfluoride (LiF), or Ag—Mg.
 8. The organic light emitting display deviceof claim 1, wherein the first electrode has a three-layer structureincluding a first transparent layer, a reflective layer on the firsttransparent layer, and a second transparent layer on the reflectivelayer, wherein each of the first transparent layer and the secondtransparent layer comprises a transparent conductive oxide, and whereinthe reflective layer comprises copper (Cu), silver (Ag), or palladium(Pd).
 9. The organic light emitting display device of claim 1, whereinthe first electrode includes a reflective layer and light emitted fromeach of the first emission layer and the second emission layer is notirradiated in a down direction through the first electrode.
 10. Theorganic light emitting display device of claim 1, wherein the firstelectrode is an anode that supplies a hole and the second electrode is acathode that supplies an electron.
 11. The organic light emittingdisplay device of claim 1, wherein the second electrode is atransmissive electrode or a semi-transmissive electrode.
 12. The organiclight emitting display device of claim 1, wherein the second electrodeis formed of a multilayer, wherein the multilayer includes at least oneof gold (Au), silver (Ag), aluminum (Al), molybdenum (Mo), magnesium(Mg), lithium (Li), calcium (Ca), lithium fluoride (LiF), indium tinoxide (ITO), indium zinc oxide (IZO), and Ag—Mg.
 13. The organic lightemitting display device of claim 1, wherein the first organic layercomprises a hole transfer layer and the hole transfer layer includes atleast one of a hole injection layer or a hole transport layer.
 14. Theorganic light emitting display device of claim 1, wherein the secondorganic layer comprises an electron transfer layer and the electrontransfer layer includes at least one of an electron injection layer orthe second electron transport layer.
 15. The organic light emittingdisplay device of claim 1, wherein the third organic layer comprises atleast one of a hole transfer layer, an electron transfer layer, a N-typecharge generation layer, or a P-type charge generation layer.
 16. Theorganic light emitting display device of claim 1, wherein at least oneof the first emission layer or the second emission layer comprises twoor more kinds of hosts and at least one dopant of a fluorescent dopantor a phosphorescent dopant.
 17. The organic light emitting displaydevice of claim 1, wherein a thickness of the first emission layer isequal to or greater than a thickness of the first organic layer.
 18. Theorganic light emitting display device of claim 1, wherein a thickness ofthe first emission layer is equal to or greater than a thickness of thesecond organic layer.
 19. The organic light emitting display device ofclaim 1, wherein a thickness of first emission layer is equal to orgreater than a thickness of the second emission layer.
 20. The organiclight emitting display device of claim 1, wherein a thickness of thesecond emission layer is equal to or greater than a thickness of thefirst organic layer.
 21. The organic light emitting display device ofclaim 1, wherein a thickness of the second emission layer is equal to orgreater than a thickness of the second organic layer.
 22. The organiclight emitting display device of claim 1, wherein a sum of a thicknessof the first emission layer and the second emission layer is equal to orgreater than a thickness of third organic layer.
 23. The organic lightemitting display device of claim 1, wherein a thickness of a thirdorganic layer is equal to or greater than a thickness of the firstemission layer.
 24. The organic light emitting display device of claim1, wherein a thickness of a third organic layer is equal to or greaterthan a thickness of the second emission layer.
 25. The organic lightemitting display device of claim 1, wherein a thickness of a thirdorganic layer is equal to or greater than a thickness of the firstorganic layer.
 26. The organic light emitting display device of claim 1,wherein a thickness of a third organic layer is equal to or greater thana thickness of the second organic layer.
 27. The organic light emittingdisplay device of claim 1, wherein a thickness of first organic layer isequal to or greater than a thickness of the second organic layer.